Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst and preparation method and application thereof
阅读说明：本技术 一种钴钼合金与钴钼混合氧化物电催化剂及其制备方法与应用 (Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst and preparation method and application thereof ) 是由 刘雨 姜德立 李娣 于 2021-08-10 设计创作，主要内容包括：本发明属于纳米材料领域,公开了一种钴钼合金与钴钼混合氧化物电催化剂及其制备方法与应用。通过简单的水热反应合成的钼酸钴前驱体,进一步将其在H-(2)/Ar气氛下煅烧得到Co-(3)Mo/CoMoO-(x)纳米片阵列电催化剂。该系列钴钼合金与钴钼混合氧化物具有较低的电荷转移电阻和析氢析氧反应的反应势垒,在电催化析氢析氧反应中均具有优越的性能。同时该催化剂成本低廉,操作简便,工艺简单,催化性能优越,为该类材料在电催化领域提供了基础应用研究。(The invention belongs to the field of nano materials, and discloses a cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst, a preparation method and an application thereof. Cobalt molybdate precursor synthesized by simple hydrothermal reaction, and further prepared by reacting the precursor in H 2 Calcining under Ar atmosphere to obtain Co 3 Mo/CoMoO x A nanosheet array electrocatalyst. The series of cobalt-molybdenum alloys and cobalt-molybdenum mixed oxides have lower charge transfer resistance and reaction barrier of hydrogen evolution and oxygen evolution reactions, and have excellent performance in electrocatalytic hydrogen evolution and oxygen evolution reactions. Meanwhile, the catalyst has low cost, simple and convenient operation, simple process and excellent catalytic performance, and provides basic application research for the materials in the field of electrocatalysisAnd (6) obtaining the finished product.)
1. A preparation method of a cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst is characterized by comprising the following steps:
(1) Cleaning the foamed nickel, and drying for later use;
(2) preparation of foamed nickel NF-based CoMoO4Precursors, i.e. CoMoO4；
Weighing Co (NO)3)2·6H2O、Na2MoO4·2H2Adding deionized water, dissolving completely to obtain a precursor solution, and placing the precursor solution in a reaction kettle; immersing the foamed nickel cleaned in the step (1) in the precursor solution, transferring the reaction kettle to an oven for hydrothermal reaction, changing the foamed nickel into light purple after the reaction is finished, then taking out the foamed nickel, washing with water and alcohol, drying in vacuum overnight, and finally annealing the precursor containing hydrate in the air to obtain the CoMoO4；
(3) Preparation of foamed Nickel NF-based Co3Mo/CoMoOxI.e. Co3Mo/CoMoOx；
Mixing the CoMoO prepared in the step (2)4Placing in an open crucible, transferring the crucible to an automatic temperature programmed tubular furnace, and heating in H2Heating to the calcining temperature in a program in the/Ar atmosphere, after the calcining is finished, naturally cooling to the room temperature, taking out, washing with water, washing with alcohol for a plurality of times, and drying to obtain the cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst, namely Co3Mo/CoMoOxWherein, CoMoOxIs represented by CoO and Co2Mo3O8Cobalt molybdenum mixed oxide.
2. The method for preparing the cobalt molybdenum alloy and cobalt molybdenum mixed oxide electrocatalyst according to claim 1, wherein in the step (1), the cleaning foam nickel is: and ultrasonically cleaning the commercial foamed nickel by using hydrochloric acid, acetone, ethanol and deionized water in sequence.
3. The method of claim 1, wherein in step (2), Co (NO) is added to the mixture of Co and Mo oxide3)2·6H2O、Na2MoO4·2H2The molar ratio of O is 1: 1, in the precursor solution, Co (NO)3)2·6H2The concentration of O is 0.029 mol.L-1，Na2MoO4·2H2The concentration of O is 0.029 mol.L-1。
4. The method for preparing an electrocatalyst made from a cobalt molybdenum alloy and a mixed oxide of cobalt molybdenum according to claim 1, wherein in step (2), the dimensions of the nickel foam are 2cm x 5 cm; the temperature of the hydrothermal reaction is 150-180 ℃, and the reaction time is 8-12 h.
5. The method for preparing the electrocatalyst made of the cobalt-molybdenum alloy and the mixed oxide of cobalt and molybdenum according to claim 1, wherein in the step (2), the annealing temperature is 300 ℃ and the annealing time is 1-2 h.
6. The method for preparing an electrocatalyst made from a cobalt molybdenum alloy and a cobalt molybdenum mixed oxide according to claim 1, wherein in step (3), H is added2The volume ratio of/Ar is 1: 9, the heating rate is 2 ℃/min, the calcining temperature is 450-750 ℃, and the calcining time is 1-3 h.
7. The method for preparing the cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst according to claim 1, wherein in steps (1), (2) and (3), the drying temperature is 60 ℃ and the drying time is 12 h.
8. An electrocatalyst made from a cobalt molybdenum alloy and a cobalt molybdenum mixed oxide, characterized in that it is prepared by the preparation method according to any one of claims 1 to 7.
9. Use of the cobalt molybdenum alloy of claim 8 in combination with a cobalt molybdenum mixed oxide electrocatalyst for electrocatalytic total hydrolysis under alkaline conditions.
Technical Field
The invention belongs to the field of nano materials, and relates to the field of electrocatalysts and preparation thereof. More particularly, relates to a preparation method and application of a high-performance alloy and mixed oxide electrocatalyst for electrochemically decomposing water to produce hydrogen and oxygen.
Technical Field
Due to exhaustion of fossil energy and serious environmental problems, demand for sustainable energy and clean energy has been increasing. Hydrogen is considered a promising renewable energy source due to its high energy density and environmental friendliness. Electrochemical water splitting is considered to be an efficient and clean hydrogen production technology due to high product purity, high efficiency and strong sustainability. Currently, Pt-based materials and Ir or Ru-based oxides are considered the most advanced electrocatalysts for HER and OER, respectively, but their widespread use in industry is hampered by high price and scarcity. The stability and activity of HER and OER catalysts are mismatched in the same electrolyte, which hinders overall water splitting performance. Therefore, it is highly desirable to design a bifunctional catalyst that is easy to manufacture and highly efficient to achieve overall water separation.
Binary transition metal oxides have very high electrochemical performance due to their complex chemical composition and synergistic effects between different metals. In particular, bimetallic Co-Mo oxides (e.g., CoMoO)4) Are considered ideal OER catalyst candidates because of the synergy between Co (excellent redox behavior) and Mo (high conductivity). However, CoMoO4The OER catalytic performance of (a) is inhibited due to its poor charge transfer efficiency and limited active sites. At the same time, CoMoO4Also, HER activity of (a) is not satisfactory, mainly due to inadequate free energy of hydrogen adsorption. Metal/metal (hydr) oxide composites with rich heterogeneous interfaces have attracted increasing attention due to the ideal electrical conductivity of the metal phase and the strong hydrolytic capacity of the metal oxide. Alloy nanoparticles, which exhibit excellent electrical conductivity and optimized hydrogen adsorption energy, are often considered candidates for designing high efficiency electrocatalysts. Feng et al and Hu et al report MoNi4/MoO2@ NF (nat. Commun.,2017,8,15437) and MoNi4/MoO3-x(ACS Appl. Mater. interfaces,2019,11,21998-22004) design of nanoarray electrocatalysts by annealing NiMoO in a reducing atmosphere4Cubic, due to MoNi 4Synergistic effect of nanoalloys and metal oxides, these being based on MoNi4The integrated nanoarrays of (a) exhibit outstanding HER activity. However, despite these advances, the reported metal/metal (hydr) oxides are limited to nickel or molybdenum based (hydr) oxides, while other metals/metal (hydr) oxides composed of Co and Mo elements with excellent conductivity and optimal reactant adsorption energyElectrocatalysts of the compounds have been rarely reported. Meanwhile, reports on the bifunctional electrocatalyst of CoMo-based alloy and metal (hydroxide) oxide for HER and OER are few, and the mechanism involved in the performance regulation of the electrocatalyst needs to be further studied.
Disclosure of Invention
The invention aims to provide a high-performance cobalt-molybdenum-based alloy and oxide three-dimensional nanosheet array structure electrocatalyst. The catalyst prepared by the method is simple in preparation method, has lower overpotential and Tafel slope and good conductivity, and the porous nanosheet array structure can greatly improve the water decomposition efficiency of the catalyst. In addition, the alloy particles generated in situ after hydrogen reduction can reduce the internal resistance of the electrode and further improve the conductivity of the electrode, thereby improving the catalytic activity of the material. Therefore, the foam nickel is used as a substrate material, the cobalt-molybdenum alloy and the cobalt-molybdenum mixed oxide are synthesized in situ, and the cobalt-molybdenum mixed oxide is applied to electrochemical total hydrolysis and has a good application prospect.
The technical scheme of the invention is as follows:
(1) cleaning the foamed nickel for later use
Ultrasonically cleaning commercial foam nickel by using hydrochloric acid, acetone, ethanol and deionized water in sequence, and drying to obtain clean foam nickel;
(2) preparation of foamed nickel NF-based CoMoO4Precursors, i.e. CoMoO4；
Weighing Co (NO)3)2·6H2O、Na2MoO4·2H2Adding deionized water, dissolving completely to obtain a precursor solution, and placing the precursor solution in a reaction kettle; and (2) immersing the foamed nickel cleaned in the step (1) in the precursor solution, transferring the reaction kettle to an oven for hydrothermal reaction, changing the foamed nickel into light purple after the reaction is finished, then taking out the foamed nickel, washing with water and alcohol, and drying in vacuum overnight. Finally, annealing the precursor containing the hydrate in the air to obtain the CoMoO4；
(3) Preparation of foamed Nickel NF-based Co3Mo/CoMoOxI.e. Co3Mo/CoMoOx；
Mixing the CoMoO prepared in the step (2)4Placing in an open crucible, transferring the crucible to an automatic temperature programmed tubular furnace, and heating in H2Heating to calcination temperature at a heating rate of 2 ℃/min in/Ar atmosphere, naturally cooling to room temperature after calcination, taking out, washing with water and alcohol for several times, and drying to obtain the cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst, namely Co3Mo/CoMoOx. Wherein, CoMoO xIs represented by CoO and Co2Mo3O8Cobalt molybdenum mixed oxide.
In step (2), Co (NO)3)2·6H2O、Na2MoO4·2H2The molar ratio of O is 1: 1, in the precursor solution, Co (NO)3)2·6H2The concentration of O is 0.029 mol.L-1，Na2MoO4·2H2The concentration of O is 0.029 mol.L-1(ii) a The size of the foamed nickel is 2cm multiplied by 5 cm; the temperature of the hydrothermal reaction is 150-180 ℃, and the reaction time is 8-12 h; the annealing temperature is 300 ℃, and the time is 1-2 h.
In the step (3), the hydrogen atom2The volume ratio of/Ar is 1: 9, the calcining temperature is 450-750 ℃, and the calcining time is 1-3 h.
In the steps (1), (2) and (3), the drying temperature is 60 ℃, and the drying time is 12 h.
The cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide prepared by the method is applied to electrocatalytic full-hydrolysis under alkaline conditions.
The product was analyzed for composition morphology using an X-ray diffractometer (XRD), a Scanning Electron Microscope (SEM) and a Transmission Electron Microscope (TEM). A three-electrode reaction device is adopted, a platinum wire is used as a counter electrode, a mercury oxide (Hg/HgO) electrode is used as a reference electrode, and the electrochemical performance of the product is tested in a 1M KOH electrolyte.
The invention has the beneficial effects that:
(1) the preparation method disclosed by the invention is composed of simple hydrothermal reaction and calcination reaction, and has the advantages of simple steps, short reaction time, convenience in operation, environmental friendliness and strong repeatability;
(2) The porous nanosheet array structure of the material increases the specific surface area of the electrode active material, provides more active sites, is beneficial to permeation of electrolyte and release of bubbles after reaction, and improves the electron transmission efficiency through the synergistic effect between the alloy and the oxide, so that the electrocatalytic activity can be further improved;
(3) the material of the invention grows on the foam nickel in situ, avoids using polymer binder, reduces the indirect contact resistance between the material and the electrode, thereby enhancing the charge transfer efficiency and quickening the reaction kinetics. These factors synergistically enhance the electrocatalytic capacity of the material in water splitting reactions.
Drawings
FIG. 1 is a diagram of the prepared CoMoO4And Co3Mo/CoMoOx-XRD diffractogram of 550 electrocatalyst.
FIGS. 2a and b are the prepared CoMoO4Scanning electron micrographs of the electrocatalyst; FIG. 2c and d are Co3Mo/CoMoOx-scanning electron micrograph of 550 electrocatalyst; FIGS. 2e and f are prepared Co3Mo/CoMoOx-550 transmission electron micrographs of electrocatalysts.
FIGS. 3a and b are the prepared CoMoO4、Co3Mo/CoMoOx-450、Co3Mo/CoMoOx-550、Co3Mo/CoMoOx-650 and Co3Mo/CoMoOxComparison of polarization curves for hydrogen evolution and oxygen evolution reactions of the-750 electrocatalyst under 1M KOH conditions.
FIGS. 4a and b are the prepared CoMoO 4、Co3Mo/CoMoOx-450、Co3Mo/CoMoOx-550、Co3Mo/CoMoOx-650 and Co3Mo/CoMoOxGraph comparing the slopes of Tafel curves for hydrogen evolution and oxygen evolution reactions of 750 electrocatalysts under 1M KOH.
Detailed Description
The invention will be further described with reference to the drawings and specific examples, but the scope of the invention is not limited thereto.
Comparative example 1
CoMoO based on Nickel Foam (NF)4Electrocatalyst (CoMoO)4) The preparation of (1):
ultrasonically cleaning foamed nickel with 3M hydrochloric acid, acetone, anhydrous ethanol and deionized water for 30min, and drying at 60 deg.C.
Weigh 0.291g Co (NO)3)2·6H2O and 0.241g Na2MoO4·2H2Adding 35mL of deionized water into the solution, stirring the mixture for 30 minutes to obtain a precursor solution, putting the foamed nickel (2cm multiplied by 5cm) into the precursor solution, transferring the precursor solution into a 50mL reaction kettle, heating the mixture at 160 ℃ for 10 hours, taking out the foamed nickel after the reaction is finished, washing the foamed nickel with water and alcohol, drying the foamed nickel at 60 ℃ for 12 hours, putting the dried foamed nickel into a tube furnace, and annealing the dried foamed nickel for 1 hour at 300 ℃ under the air condition to obtain the CoMoO4。
Example 1
Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst (Co) with foamed Nickel (NF) as substrate3Mo/CoMoOx-550) preparation:
ultrasonically cleaning foamed nickel with 3M hydrochloric acid, acetone, anhydrous ethanol and deionized water for 30min, and drying at 60 deg.C.
Weigh 0.291g Co (NO)3)2·6H2O and 0.241g Na2MoO4·2H2Adding 35mL of deionized water into the solution, stirring the mixture for 30 minutes to obtain a precursor solution, putting the foamed nickel (2cm multiplied by 5cm) into the precursor solution, transferring the precursor solution into a 50mL reaction kettle, heating the mixture at 180 ℃ for 12 hours, taking out the foamed nickel after the reaction is finished, washing the foamed nickel with water and alcohol, drying the foamed nickel at 60 ℃ for 12 hours, putting the dried foamed nickel into a tube furnace, and annealing the dried foamed nickel for 1 hour at 300 ℃ under the air condition to obtain the CoMoO4。
The CoMoO prepared in the above way4Placing in a crucible, transferring the crucible to an automatic temperature programmed tube furnace, in H2Heating to 550 ℃ at the heating rate of 2 ℃/min in an/Ar (v: v ═ 1:9) atmosphere, calcining for 2h, naturally cooling to room temperature after calcining, taking out, washing with water and alcohol, and drying at 60 ℃ for 12h to obtain the product Co3Mo/CoMoOx-550。
Example 2
Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst (Co) with foamed Nickel (NF) as substrate3Mo/CoMoOx-450) preparation:
the preparation method of the electrocatalytic material is basically the same as that of the example 1, except that: at H2Calcining for 2 hours at the temperature of 450 ℃ in the Ar atmosphere.
Example 3
Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst (Co) with foamed Nickel (NF) as substrate3Mo/CoMoOx-650) preparation:
the preparation method of the electrocatalytic material is basically the same as that of the example 1, except that: at H 2Calcining at 650 ℃ for 2h in an Ar atmosphere.
Example 4
Cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrocatalyst (Co) with foamed Nickel (NF) as substrate3Mo/CoMoOx-750) preparation:
the preparation method of the electrocatalytic material is basically the same as that of the example 1, except that: at H2Calcining at 750 ℃ for 2h in an Ar atmosphere.
Electrocatalytic activity experiment of cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrode material
KOH solution with the concentration of 1 mol per liter is used as electrolyte, a three-electrode reaction device is adopted, a platinum wire is used as a counter electrode, Hg/HgO is used as a reference electrode, the scanning speed is 5mV/s, and the electrocatalytic water decomposition performance of the cobalt-molybdenum alloy and cobalt-molybdenum mixed oxide electrode material in the solution is tested.
Examples characterization analysis of cobalt molybdenum alloys and cobalt molybdenum mixed oxide catalysts
FIG. 1 is a diagram of the prepared CoMoO4And Co3Mo/CoMoOxXRD diffraction pattern of-550 electrocatalyst, from which CoMoO can be seen4The diffraction peak in (1) corresponds well to the CoMoO4Standard card (PDF #21-0868), at H2Co formed after reduction in/Ar atmosphere3Mo/CoMoOx-550 and standard cards (PDF #71-1423), (PDF #43-1004) and (P)DF #29-0488) corresponded well.
FIGS. 2a and b are the prepared CoMoO4Scanning electron micrographs of the electrocatalyst, from FIGS. 2a, b, it can be seen that CoMoO 4Presenting a three-dimensional inter-crosslinked nano-array structure composed of nano-flakes; FIG. 2c and d are Co3Mo/CoMoOxScanning electron micrographs of the electrocatalyst 550, from figures 2c, d it can be seen that the reduced nanosheet surface is accompanied by the appearance of small particles and irregular pores; FIG. 2e, f are Co3Mo/CoMoOx-550 transmission electron microscope photograph of electrocatalyst, from fig. 2e, f it can be seen that the reduced surface of nanosheet has particles and irregular pores.
FIGS. 3a and b are the prepared CoMoO4、Co3Mo/CoMoOx-450、Co3Mo/CoMoOx-550、Co3Mo/CoMoOx-650 and Co3Mo/CoMoOxComparison of polarization curves for hydrogen evolution and oxygen evolution reactions of the-750 electrocatalyst under 1M KOH conditions. It can be seen from the figure that reduction at different temperatures can increase the monomer CoMoO4The electrocatalyst activity of (1), wherein the electrocatalyst Co after reduction at 550 ℃3Mo/CoMoOxBest-550 performance, with a current density of 10mA cm-2The corresponding hydrogen evolution and oxygen evolution overpotentials were 23mV and 263mV, respectively.
FIGS. 4a and b are the prepared CoMoO4、Co3Mo/CoMoOx-450、Co3Mo/CoMoOx-550、Co3Mo/CoMoOx-650 and Co3Mo/CoMoOxGraph comparing the slopes of Tafel curves for hydrogen evolution and oxygen evolution reactions of 750 electrocatalysts under 1M KOH. From the figure, Co is known3Mo/CoMoOx-550 electrocatalyst having specific Co ratio3Mo/CoMoOx-450、Co3Mo/CoMoOx-650、Co3Mo/CoMoOx750 and CoMoO4A smaller tafel slope.